Hub mounting



April 12, 1966 F. P. RoDwlcK 3,245,476

HUB MOUNTING Filed Oct. 26, 1964 ETI/anion' n P Roda/c United States Patent O M 3,245,476 HUB MOUNTING Frank P. Rodwiclr, St. Louis, Mo., assignor to Knapp- Monarch Co., St. Louis, Mo., a corporation of Delaare Filed Oct. 26, 1964, Ser. No. 406,477 2 Claims. (Cl. 170--173) This invention relates to improved mounting means for securing a hub of a rotating device on a shaft and it particularly relates to improved means for securely mounting a plastic fan blade hub on a rotating motor shaft.

Generally speaking, there is always a problem associated with mounting a plastic part on a metallic part as a result of the wide variance between the coefficients of expansion of each of such parts and also as a result of cold flow that occurs with plastic material, and particularly in the case of thermoplastic materials. One area in which considerable difficulty has been encountered in obtaining a suitable mounting of a plastic part on a metallic part is in the mounting of a plastic fan blade on a metallic motor shaft. One significant problem associated in mounting a plastic fan blade on a motor shaft is that it is important that the fan blade be tightly secured on the shaft in order to avoid an excessively high noise level, such as would be caused by wobbling of the fan on the shaft during rotation. It is also very important in electric fans that the motor shaft be extremely straight, desirably in the range of .000 to .005 inch deviation of total indicator reading. If the type of mounting used causes a deviation from this desired straightness, the fan would have an eccentric rotation and cause vibration. This would seriously shorten the life of the motor bearings, would cause an excessively high noise level while the fan is operating, and would cause excessive wear in the gear mechanism of the fan.

Although some available motor shaft mountings may satisfy one or another of the foregoing requirements, no known mounting satisfies these requirements while at the same time providing a highly economical construction for the mounting. One of the primary advantages of utilizing a molded plastic fan blade is the economy of its construction. Therefore, in assemblies where the construction cost is increased as a result of an expensive type of mounting, as is now required for use with a plastic fan blade, the economic advantage of using a plastic fan blade may be lost.

It is therefore an important object of this invention to provide an improved mounting for plastic fan blades wherein economy of construction and assembly is effected and wherein the disadvantages of existing mounting constructions are substantially avoided.

It is also an object of this invention to provide an improved plastic fan blade mounting wherein the fan blade is maintained in rigid or firm securement on the motor shaft, to 'thereby substantially avoid undesired vibrations or movement of the fan blade on the motor shaft during operation.

It is a further object of this invention to provide an improved mounting for a plastic fan blade wherein the mounting arrangement also assists in maintaining the motor shaft in a straight condition, to thereby substantially avoid the adverse effects of eccentric rotation of the fan blade.

Further purposes and objects of this invention will appear as the specification proceeds.

A particular embodiment of the present invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a front elevational view of a fan blade utilizing my improved mounting construction;

FIGURE 2 is an enlarged fragmentary sectional view taken along the line 2 2 of FIGURE l; and

FIGURE 3 is an end view taken looking from the right of FIGURE 2.

Referring to the drawings, a molded, integral fan blade 10 is shown mounted upon a metallic motor shaft 12. The fan 10 defines a plurality of individual blades or paddles 14 which project outwardly from a fan hub 16. The shaft 12 extends from a motor (not shown) that drives or rotates the fan 10 at a relatively high rotational speed. At this speed, it is important that the fan 10 be held in rigid or firm securement on the motor shaft 12 and that the rotation of the fan be substantially free of eccentricity.

The cylindrical hub 16 defines an outer cylindrical hub wall 26, a transverse wall 18 of irregular cross-section as seen in FIGURE 2, and a tubular central sleeve 22 coaxial of hub wall 26. The forward facing side of transverse wall 18 denes depressed annular recess or well 20. The elongated bore 24 defined by sleeve 22 receives shaft 12. The terminus of sleeve 22 projects rearwardly of the axial extent of hub wall 26. A plurality of rigidifying ribs 28 extend radially between hub wall 26 and sleeve 22, thereby defining a plurality of hollows 30 rearwardly of transverse wall 18. Although the fan 10 may be constructed of any material commonly used for fan blade construction, including metal, it is preferred for economy of construction that the fan be made of a plastic material. Preferably, the fan blade 10 is constructed of a thermoplastic material, such as propylene or styrene acrylonitrile.

The elongated bore 24 is formed with such dimensions as to slidably receive therein the motor shaft 12, to thereby provide means toward the end of a firm and rigid mounting of the fan blade 10 upon the shaft 12. The forward or outer terminus 32 of the motor shaft 12 has a threaded portion 34 and also a screwdriver-receiving slot 36 defined at its extremity.

In positioning the fan 10 upon the shaft 12, a retaining ring or stop washer 38, of C-shape for snap mounting, is first mounted upon the shaft 12 by snapping into a suitable groove 40, that is spaced from the threaded end of the shaft 12. The hub 16 is slid onto the shaft 12 until the terminus 42 of sleeve 22 abuts the washer 38, which acts to stop further movement of the fan 10 along the shaft 12. The axial length of tubular part 22 is greater than the spacing between groove 40 and the threaded end portion of shaft 12. A resilient toothed lock washer 44 and screw nut 46 on threaded portion 34 of the shaft 12 complete the assembly.

For tightening the nut 46 upon the shaft 12, a screwdriver may merely be inserted into the slot 36 at the outer end of vthe shaft 12, and any appropriate means may be used for tightening up the nut 46 upon the threaded portion 34. This clamps the lock washer 44 between transverse wall 18 and nut 46, to secure the fan blade 10 on the shaft 12.

The threads on the shaft 12 and in the nut 46 may be either left-handed or right-handed, depending upon the rotation of the fan 10. If the fan rotates in a clockwise direction, left-handed threads are utilized, while if the rotation of the fan is in a counterclockwise direction, right-handed threads are utilized. The reason for this is that this provides for self-tightening of the nut 46 upon the threaded portion 34 while the fan is operating. This is considered important sinceI plastic materials, particularly thermoplastic materials, are subject to cold ow, so that the initial force, such as compression applied to tubular part 22 is likely to vary with time. Therefore, Iby providing a self-tightening nut, the rotation of the fan 10 will tend to maintain the nut and lock washer 44 tightly against the hub body 16. It is also important that the lock washer 44 be of the resilient expansible type, so that there is a substantial difference between its overall thickness while in the free condition and while in its compressed condition, and preferably, this resilience provides a range of expansion of about .020 inch.

. The'resiliency of the lock washer 44, together with a substantially high torque on the tightening nut 46 (preferably about inch-pounds) assures a tightening force which vwill hold the tubular portion 22 of the fan hub 16 in compression -between the stop ring 38 and the lock washer 44. A compression force is maintained even after cold ow, as a result of the compressibility or resiliency of the lock Washer 44 and the self-tightening of the nut 46 upon the shaft 12. By maintaining the hub 16 in compression, the motor shaft 12 is maintained iu a substantially straight condition and generally within the desired range of .000 to .005 inch deviation of total indicator reading. If a groove 40 were provided in the shaft 12, and if no compressive force were involved in the construction of the mounting, the motor shaft 12 would be weakened and would bend quite readily. The main- 1tenance of the central portion 22 in compression thus assists in maintaining the straightness of the motor shaft 12.

The isolation of cylindrical hub wall 26 from tubular part 22 by spacing therefrom except through radial ribs 28 insures that the axial compression forces on tubular part 22 are normally isolated from hub wall 26, thereby avoiding distortion in the mounting for the blades 14.

A further advantage of my construction is that 4the screwdriver slot 36 enables the nut 46 to be removed or tightened upon the shaft 12 without the necessity of gripping or holding a paddle 14. Only a simple household screwdriver and a simple household tool such as pliers are needed for manipulating the nut 46 and for restraining the slotted end of the shaft 12 from moving, with both operations occurring at only one end of shaft 12. It is desirable not to restrain the fan 10 by holding one of the paddles 14, so as to avoid any strains upon the fan 10.

While in the foregoing, there has been provided a detailed description of a particular embodiment of the present invention, it is to be understood that all equivalents obvious to those having skill in the art are to be included within the scope of the invention as claimed.

What I claim and desire to secure by Letters Patent 1. A fan and shaft construction comprising a metal drive shaft, a plastic hub, at least one plastic blade con nected to said hub, said shaft having a slotted and threaded outer end with a resilient lock washer thereon and a circumferential groove spaced from said end, a retaining washer securely mounted in said groove, said hub comprising a central tubular mounting portion with a bore therethrough, the part of the shaft between the retaining washer and the lock Washer being received in said bore, a nut threadaibly secured on the outer end of the shaft compressing the hub between the washers and securing the hub to the shaft, said hub further comprising a coaxial cylindrical hub wall supporting said blade and spaced from and surrounding the tubular mounting portion, and a transverse wall portion connecting the cylindrical hub wall and the tubular mounting portion and including a depressed annular recess which surrounds the nut and lock Washer.

2. A fan and shaft. construction as in claim 1 wherein the threads on the end of the shaft are selected so as to be self tightening Where the shaft is driven in a normal direction of rotation.

References Cited by the Examiner UNITED STATES PATENTS 856,586 6/1907 Humphrey et al 170-173 1,318,805 10/1919 Rupp 170-173 1,489,841 4/1924 MacDonald 170-16047 1,493,066 5/1924 Caldwell et al. 170-160.54 1,797,068 3/1931 Bocksruker 170-173 2,164,744 7/1939 Huth 170 160.53 2,313,105 3/1943 Walls 170-177 X 2,346,552 4/1944 BrOtZ.

2,380,770 7/ 1945 McFarland. 2,486,619 11/ 1949 Troxler. 2,950,082 8/1960 McVeigh. 2,993,544 7/1961 Carlson l70-l60.54

FOREIGN PATENTS 207,625 3/1956 Canada. 1,149,937 7/1957 France.

SAMUEL LEVINE, Primary Examiner.

JULIUS E. WEST, Examiner.

E. A. POWELL, Assistant Examiner. 

1. A FAN AND SHAFT CONSTRUCTION COMPRISING A METAL DRIVE SHAFT, A PLASTIC HUB, AT LEAST ONE PLASTIC BLADE CONNECTED TO SAID HUB, SAID SHAFT HAVING A SLOTTED AND THREADED OUTER END WITH A RESILIENT LOCK WASHER THEREON AND A CIRCUMFERENTIAL GROOVE SPACED FROM SAID END, A RETAINING WASHER SECURELY MOUNTED IN SAID GROOVE, SAID HUB COMPRISING A CENTRAL TUBULAR MOUNTING PORTION WITH A BORE THERETHROUGH, THE PART OF THE SHAFT BETWEEN THE RETAINING WASHER AND THE LOCK WASHER BEING RECEIVED IN SAID BORE, A NUT THREADABLY SECURED ON THE OUTER END OF THE SHAFT COMPRESSING THE HUB BETWEEN THE WASHERS 